This invention relates to devices for the purification and reclamation of lubricating mineral oils. A large part of contaminants found in used lubricating oil is constituted by foreign materials such as water condensed from air moisture, products of fuel combustion, fuel dilution, and products resulting from chemical action within the system such as products of partial decomposition of oil and incomplete combustion of fuel which have a lower boiling point than the mineral lubricating oil. In the reclamation process of used lubricating oil, these products are boiled off under suitable temperature conditions. Normally, a certain amount of purification is achieved in an internal combustion engine which is allowed to run at a relatively high temperature. In an automobile, truck, tractor, or heavy equipment engine which is often run for a short period of time and in which the temperature is very efficiently limited by a pressurized water cooling system, the heat purification process is practically non-existent. These volatile contaminants are not retained by conventional oil filters and contribute to the early deterioration of the lubricating agent. The combination of a mechanical filter and evaporation system for the on-line purification of lubricating oil in an internal combustion engine would greatly increase the period between oil changes and improve the efficiency of the power system.